Respiratory development

Question 1

Laryngotracheal groove develops from what?

Answer 1

Ventral wall of primitive pharynx caudal to 4th pair of pharyngeal pouches.

Question 2

What does the laryngotracheal groove deepen to form?

Answer 2

Respiratory diverticulum

Question 3

What respiratory structures develop from the endoderm?

Answer 3

Epithelium, glands of larynx, trachea, bronchi, pulmonary epithelium

Question 4

What respiratory structures develop from the splanchnic mesenchyme of foregut?

Answer 4

Connective tissue, cartilage, smooth muscle

Question 5

Laryngeal cartilages develop from what?

Answer 5

Cartilages of 4th and 6th pharyngeal arches

Question 6

What do the 4th and 6th pharyngeal arches develop from?

Answer 6

Mesenchyme derived from NEURAL CREST CELLS

Question 7

What do laryngeal muscles develop from?

Answer 7

Myoblasts of 4th and 6th pairs of pharyngeal arches

Question 8

What nerves innervate laryngeal muscles?

Answer 8

Superior laryngeal (sensory above vocal cord) and recurrent laryngeal (sensory below and all motor)
Origin: vagus nerve

Question 9

What gives rise to epiglottis?

Answer 9

Hypobranchial eminence

Question 10

What is larynx epithelial lining derived from?

Answer 10

Endoderm

Question 11

What is the trachea formed from?

Answer 11

Laryngotracheal tube distal to larynx

Question 12

What parts of trachea are of endodermal origin?

Answer 12

Tracheal glands (develop from ingrowth of surface epithelium)

Question 13

What parts of trachea are derived from splanchnic mesoderm?

Answer 13

Cartilage, connective tissue, muscles

Question 14

Tracheoesophageal fistula

Answer 14

–Abnormal communication (fistula) between trachea and esophagus

Question 15

What is the most common anomaly of lower respiratory tract?

Answer 15

Tracheoesophageal fistula

Question 16

What is tracheoesophageal fistula commonly associated with?

Answer 16

Esophageal atresia

Question 17

What is esophageal atresia?

Answer 17

Blind-ended esophagus

Question 18

What causes tracheoesophageal fistula?

Answer 18

Abnormal partitioning between tracheoesophageal septum causing abnormal communication between trachea and esophagus

Question 19

How can pneumonia or pneumonitis occur from tracheoesophageal fistula?

Answer 19

Food or gastric contents may enter lungs

Question 20

How can polyhydramnios occur from tracheoesophageal fistula?

Answer 20

Amniotic fluid accumulates because amniotic fluid can’t pass to stomach and intestines for absorption and transfer via placenta to mother’s blood

Question 21

How do bronchopulmonary segments develop?

Answer 21

Laryngotracheal groove–> respiratory diverticulum –> tracheal bud –> primary bronchial buds –> secondary bronchial buds –> segmental branches

Question 22

What do primary bronchial buds grow into?

Answer 22

Pericardioperitoneal canals

Question 23

What are epithelium and bronchial glands derived from?

Answer 23

Endoderm

Question 24

What parts of bronchi are derived from splanchnic mesoderm?

Answer 24

Cartilaginous plates, bronchial smooth muscle, connective tissue, pulmonary connective tissue and capillaries

Question 25

What is the visceral pleura derived from?

Answer 25

Splanchnic mesoderm

Question 26

What is the parietal pleura derived from?

Answer 26

Somatic mesoderm

Question 27

Azygous lobe

Answer 27

Part of superior lobe of right lung that grows medial to azygos vein instead of lateral to it

Question 28

Agenesis of lungs

Answer 28

Failure of bronchial bud to develop can be unilateral or bilateral

Question 29

What is lung hypoplasia typically associated with (2 different things)?

Answer 29

Congenital diaphragmatic hernia or oligohydramnios

Question 30

Potter syndrome

Answer 30

Pulmonary hypoplasia, bilateral renal agenesis, caused by oligohydramnios

Question 31

How can oligohydramnios cause pulmonary hypoplasia?

Answer 31

Uterine wall compresses fetal thorax causing lung hypoplasia

Question 32

What can cause oligohydramnios?

Answer 32

Bilateral renal agenesis causes lack of urine production and reduces amount of amniotic fluid present

Question 33

Four stages of lung maturation

Answer 33

1. Pseudoglandular period 2. Canalicular period 3. Terminal sac period 4. Alveolar period

Question 34

Pseudoglandular period

Answer 34

- -6-16 wks - -Ductal elements (bronchi and terminal bronchioles) of lung development - -No alveoli present

Question 35

Canalicular period

Answer 35

- -16-26 weeks - -Bronchi and terminal bronchioles enlarge and respiratory bronchioles and alveolar ducts develop - -Vascularization - -Respiration is possible because of developing alveoli

Question 36

What direction do respiratory and alveolar ducts develop from?

Answer 36

Cranial to caudally

Question 37

Terminal sac period

Answer 37

- -26 wks to birth - -Type 1 alveolar cells form - -Blood-air barrier develops - -Type II alveolar cells start to secrete surfactant

Question 38

What is infant survival dependent on in terminal sac period?

Answer 38

Adequate vasculature and surfactant

Question 39

Type I alveolar cell origin

Answer 39

Squamous epithelium of endodermal origin

Question 40

Type II alveolar cells

Answer 40

Secrete pulmonary surfactant

Question 41

When does surfactant secretion begin?

Answer 41

Begins at 20 weeks, not sufficient until 26-28 wks.

Question 42

What can accelerate surfactant production during pregnancy?

Answer 42

Glucocorticoids

Question 43

Alveolar period

Answer 43

- -Late fetal period to year 8 of childhood - -Maturation of alveoli - -Increase respiratory bronchioles and primitive alveoli

Question 44

What do fetal breathing movements do?

Answer 44

Stimulate lung development and facilitates development of respiratory musculature

Question 45

How many alveoli are present at birth? What do they increase to by age 3? How long do we continue to develop new alveoli?

Answer 45

150 million. 300 million. 8 years old.

Question 46

What is lung fluid in fetus derived from?

Answer 46

Amniotic fluid, lung tissue itself, secretions by tracheal and bronchial glands

Question 47

How does removal of lung fluid occur at birth?

Answer 47

1. Through mouth and nose by pressure on thorax during delivery 2. Into pulmonary capillaries 3. Into lymphatics

Question 48

Congenital lung cysts

Answer 48

Formed by dilation of terminal bronchioles due disturbance in bronchial development during late fetal life

Question 49

What do lungs with congenital lung cysts look like?

Answer 49

Honeycomb appearance

Question 50

What accounts for 20% of all infant deaths during newborn period

Answer 50

Respiratory distress syndrome

Question 51

Hyaline membrane disease/respiratory distress syndrome cause and location?

Answer 51

Deficiency of surfactant and injury to alveolar wall causing protein-rich, fibrin-rich exudate derived from injured pulmonary epithelium and circulating blood substance. Located in alveolar space and forms hyaline membrane

Question 52

What is difference between newborn lungs and stillborn lungs?

Answer 52

Stillborn lungs sink because they contain fluid, not air. Newborn lungs contain air and float in water.